Method and device in a paper machine for transfer of the web from the former section to the press section

ABSTRACT

A method in a paper machine for transferring a paper web from a wet wire in a former section to a pick-up fabric or an equivalent transfer fabric of a press section, including the steps of forming a pick-up point on the wet wire and separating an edge strip from at least one edge of the web prior to the pick-up point by means of at least one cutting device. The method further includes separating the web from the wet wire and passing the web onto the pick-up fabric at the pick-up point. The method also includes applying a pressure difference to the at least one edge strip through the wet wire or the pick-up fabric at or after the pick-up point to cause the at least one edge strip to either follow the wet wire or become separated from the pick-up fabric after the pick-up point and to be placed in a broke system arranged beneath the paper machine.

FIELD OF THE INVENTION

The invention concerns a method in a paper machine for transfer of thepaper web that was formed in the former section to the press section. Inthe method, a pick-up point is formed in connection with the wet wire ofthe former section, the paper web being transferred in the area of thepick-up point, using a difference in pressure, onto a pick-up fabric oran equivalent transfer fabric. Before the pick-up point, edge strips areseparated from one or both edges of the web by means of cutting grooves,the web between the edge strips or the web being separated from the wetwire at the pick-up point and being passed on support of the pick-upfabric or equivalent to the press section in the paper machine.

Further, the invention concerns a device in a paper machine for transferof the paper web that was formed in the former section to the presssection. In the paper machine, a pick-up point for the paper web isformed in connection with the wet wire of the former section, at whichpick-up point the paper web is transferred, while making use of adifference in pressure, onto a pick-up fabric or an equivalent transferfabric. Before the pick-up point, cutter devices are arranged by whosemeans edge strips are separated from one or both edges of the web. Theweb between the edge strips is separated from the wet wire at thepick-up point and is passed on the pick-up fabric or equivalent to thepress section in the paper machine.

BACKGROUND OF THE INVENTION

Increased running speeds of paper and board machines cause new problemsto be solved, which problems are mostly related to the runnability ofthe machine. At present, speeds of up to about 1600 to 1700 meters perminute are employed in paper machines. At these speeds, so-called closedpress sections, which comprise a compact combination of press rollsfitted around a smooth-faced center roll, as a rule, still operatesatisfactorily. As examples of such press sections should be mentionedthe current assignee's Sym-Press II™ and Sym-Press O™ press sections.

In recent years, as running speeds of printing-paper machines, runningspeeds as high as about 40 meters per second=2400 meters per minute havebeen contemplated. Achievement of speeds as high as this, in particularin wide machines, provides ever more difficult problems to be solved,some of the most important of which are runnability of the machine andadequate water drain capacity at a high web speed. In a correspondingway, in board machines (basis weight of web>100 grams per sq. meter),attempts are made to raise the present-day web speeds (8 to 15 metersper second) to a level of 15 to 25 meters per second.

When running speeds of paper machines are increased, the problems ofrunnability of a paper machine are also encountered with increasedemphasis, because a web with high water content and low strengthespecially does not endure the dynamic forces arising from high webspeeds and changes in the running direction of the web, but web breaksand other interference in the operation arise, which will be describedin more detail later and which produce standstills or faults of qualityin the paper. In a modern printing-paper machine, the cost of breakstandstill time is currently of an order of 50,000 FIM per hour.

In prior-art press sections, the web is, as a rule, passed from theforming wire into the first press nip on a pick-up felt, which alsooperates as a press fabric that receives water in the first press nip,which nip is either a roll nip or an extended nip. In the first pressnip, it is necessary to use a relatively high compression pressure andto deal with large quantities of water, and it is one drawback arisingfrom this that the outer face of the press felt tends to be contaminatedand its porous fabric structure to be partly blocked. Attempts are madeto prevent this by means of efficient felt conditioning devices, whichare, however, components that are quite expensive, spacious, and consumean abundance of energy. A further drawback of the press felts used inprior-art press sections is their effect of rewetting the web.

In a way known from the prior art, in the vicinity of the wet wire,before the pick-up point, devices for cutting of edge strips off theweb, i.e. so-called edge spray cutters, are fitted, by whose means, bymeans of water jets applied to the web placed on the wet wire, narrowedge strips are cut off from both edges of the web so that a web ofuniform width with whole and good edges is obtained to be passed to thepress section. As is known from the prior art, the cutters of edgestrips can be provided with position regulation devices, by whose meansthe web cutting width can be adjusted and regulated within certainlimits.

By means of the present invention, attempts are made to eliminateproblems related to the cutting of the edges of the paper web which havebeen encountered in the current assignee's test machine when running ata high speed and in particular with webs of relatively low basis weight.When the running speed of the test machine was higher than about 1500meters per minute, the edge strips that were cut off from the paper webin the wire part before the pick-up roll tended to follow the pick-upfelt after the pick-up roll, instead of following the wet wire. Thistook place in particular when the permeability of the pick-up felt waslow. The permeability of the pick-up felt can be low also when new,because of its structure, and in particular when the felt is compactedand contaminated as a result of prolonged service life, as was describedabove. If the edge strips of the paper web enter fully or partially intothe press nips, they cause interference with the runnability and producefiber strings that damage the press felts and the extended-nip belts.

The above problems related to the cutting of the edges of a paper weband the other difficulties are emphasized further when the web speedapproaches 2000 meters per minute and exceeds the speed. It is one ofthe problems of runnability that, owing to these problems, in the presssection it is not possible to employ steam boxes in order to enhance thedewatering. It has not been possible to a major extent to reduce theseproblems by means of regulation of the cutting width of the water jetdevices that cut the edges of the paper web, i.e. of the edge spraycutters, or by means of regulation of the suction width in a pick-uproll.

It is probably one of the reasons for the problems related to thecutting of the edges of the paper web that replacement air flows intothe opening nip between the forming wire and the pick-up felt morereadily through the forming wire than through the pick-up felt. Sincethe width of the strip torn off from the edge is approximately equal tothe width of the end seals of the suction zone in the pick-up roll,these seals may prevent the flow of replacement air through the holes inthe mantle of the pick-up suction roll at the location of the seals.This is also indicated by the fact that it can also be frequently seenin production machines that the edge strips are folded double across awidth of about 30 mm after the pick-up point before the edge stripknock-off jets.

OBJECTS AND SUMMARY OF THE INVENTION

By means of the present invention, attempts are made to provide novelsolutions for the problems dealt with above, in particular when the webspeed is higher than 1500 meters per minute and, as a rule, in a range1500 to 2500 meters per minute.

It is a particular object of the invention to provide a method and adevice of the sort concerned by whose means it can be ensured thateither the edge strips run after the pick-up point along with the wetwire or the edge strips are separated from the pick-up felt so that theedge strips can be passed in a controlled way, by the effect ofcentrifugal forces and, if necessary, by means of knock-off watershowers, into a wire pit or equivalent placed underneath.

In view of achieving the objectives stated above and those that willcome out later, the method in accordance with the invention fortransferring a paper web from a wet wire in a former section to apick-up fabric or an equivalent transfer fabric of a press sectionincludes forming a pick-up point on the wet wire and separating an edgestrip from at least one edge or both edges of the web prior to thepick-up point by means of at least one cutting device. The web isseparated from the wet wire and passed onto the pick-up fabric at thepick-up point. The method further includes applying a pressuredifference to the edge strips through the wet wire or the pick-up fabricat or after the pick-up point to cause the edge strips to either followthe wet wire or become separated from the pick-up fabric after thepick-up point and to be placed in a broke system arranged beneath thepaper machine.

On the other hand, the paper machine in accordance with the invention inwhich a paper web is transferred from a wet wire in a former section toa pick-up fabric in a press section in a running direction of the webincludes a pick-up point located on the wet wire and at least one cutterdevice arranged in association with the wet wire before the pick-uppoint in the running direction of the web for separating an edge stripfrom at least one edge or both edges of the web. The paper machine alsoincludes means for transferring the web from the wet wire to the pick-upfabric at the pick-up point and means for applying a pressure differenceto the edge strips through the wet wire or the pick-up fabric at orafter the pick-up point to cause the edge strips to either follow thewet wire or become separated from the pick-up fabric after the pick-uppoint and to be placed in a broke system arranged beneath the papermachine.

In a device in accordance with a preferred embodiment of the invention,the edge strips of the web are kept in contact with the wet wire byvacuum devices of a width substantially equal to the width of the edgestrips. An alternative with a full-width vacuum device is also possible,in which case intensifying suction zones can be fitted in the areas ofthe edge strips. A full-width alternative of a vacuum device may beprovided with instantaneous switching off of the vacuum in the middlearea as soon as threading of the web starts. By means of this method anddevice it is possible to improve the quality of the tip of the web inthreading, and also in cutting-off the web, when the vacuum of thevacuum device is switched on at a suitable stage.

In accordance with a second preferred embodiment of the invention,pressure devices of a width substantially equal to the width of the edgestrips and placed after the pick-up roll and fitted at the location ofthe edge strips are used, by means of which pressure devices the edgestrips are separated from the pick-up felt and passed, for example, bymeans of a guide plate or plates down to the broke system.

In accordance with a third preferred embodiment of the invention,pressure zones are used, which are placed outside the vacuum zone of thepick-up roll at both sides of the vacuum zone and which have been fittedat the location of the edge strips and which prevent portions placedoutside the paper web proper to be passed to the press section fromfollowing the pick-up felt.

In a fourth embodiment of the invention it is possible to arrange a blowdevice of full width inside the loop of the wet wire after the pick-uppoint, by means of which blow device the web of full width can beseparated from the wet wire when the web is not passed to the presssection, e.g., in the event of a disturbance in operation.

The alternative embodiments of the method and the device mentioned abovecan be used each of them alone or as a suitable combination, always asnecessary.

The present pick-up method and devices are, as a rule, applied in papermachines whose speed is higher than ˜1500 meters per minute. A pick-upmethod and a device in accordance with the present invention areparticularly useful, and in many cases even indispensable, in papermachines whose speed range is 1700 to 2500 meters per minute, in whichspeed range the problems that are supposed to be eliminated by means ofthe present invention occur with more emphasis when the speeds that areused become higher.

By means of the method and the device in accordance with the invention,it is possible to ensure in all different situations of operation, alsoat very high speeds, that the edge strips do not enter into the presssection along with the pick-up felt, but the edge strips either followthe wire directly after the pick-up point and fall down into the brokesystem placed underneath, or are separated from the pick-up felt at thelatest in or after the pick-up zone and are passed, for example, bymeans of a guide plate, into the broke system. Further, in a preferredembodiment of the invention, it is ensured that the web of full width isseparated from the wet wire in a situation of operation in which the webis not passed to the press section, for example, in the event of adisturbance in operation, but the web is passed from the wet wiredirectly into the broke system.

In the following, the invention will be described in detail withreference to some environments of application and exemplifyingembodiments of the present invention illustrated in the figures in theaccompanying drawing, the invention being in no way strictly confined tothe environments or embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not meant to limit the scope of the invention as encompassed bythe claims.

FIG. 1 shows an embodiment of the invention having devices for guidingand transferring the edge strip of the web.

FIG. 2 shows another embodiment of the invention having two successiveextended-nip presses and a particular arrangement of pick-up of the webfrom the lower wet wire.

FIG. 3 shows a device of the present invention as viewed in thedirection A indicated in FIG. 1 and in the direction B indicated in FIG.2.

FIG. 4 shows a second device of the present invention as viewed in thedirection C indicated in FIG. 1 and in the direction D indicated in FIG.2.

FIG. 5 shows a third device of the present invention as viewed in thedirection E indicated in FIG. 2.

FIG. 6 shows another embodiment of the present invention.

FIG. 7 is a central sectional axial view of the embodiment of theinvention shown in FIG. 6 as viewed in the direction G indicated in FIG.6.

FIG. 8 is a modification of the embodiment of the invention shown inFIG. 7.

FIG. 9 is a partial central axial sectional view of the embodiment ofthe invention shown in FIG. 6 as viewed in the direction F indicated inFIG. 6.

FIG. 10 is a modification of the embodiment of the invention shown inFIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To begin with, reference being made to FIGS. 1 and 6, a typicalenvironment of application of the invention will be described, whichincludes a compact press section marketed by the current assignee withthe trade mark SymPress II B™. It should be emphasized also in thisconnection that the invention is not confined to the environments ofapplication illustrated in the different figures, but many otherenvironments can also be concerned equally well.

The paper machine as shown in FIGS. 1 and 6 comprises a former section1, a press section 2, and a dryer section 3. Of the former 1, just thefinal end is shown, and of the dryer section 3 just the initial end isshown. On the wet wire 10 of the former 1, the web W is brought over thesuction zone 11 a of the suction roll 11 onto a downwards inclined runof the wet wire 10, which run extends down to the wire drive roll 12. Onthis downwards inclined run of the wire 10 the paper web W is separatedfrom the forming wire 10, which wire is, for example, a carrying lowerwire in a twin-wire former, and the web is transferred by means of thevacuum in the suction zone 21 a of the pick-up suction roll 21 onto thepick-up felt 20 at the point P. On the lower face of the pick-up felt 20the web W is transferred into the first nip N₁ in the press section, inwhich the pick-up felt 20 operates as an upper fabric. The first nip N₁is formed by an upper press suction roll 22, in which there aresuccessive suction zones 22 a and 22 b, and by a lower, hollow-faced 32press roll 31. Through the first nip N₁, a lower belt 30 runs, whichreceives water and from which the web W is separated so as to follow theupper felt 20, with the aid of the vacuum in the suction zone 22 a ofthe suction roll 22.

In FIGS. 1 and 6, the second nip N₂ in the press section is formedbetween the suction roll 22 and a smooth-faced 26 center roll 25. Thesecond roll nip N₂ is placed on the suction zone 22 b of the suctionroll 22. After the nip N₂ the web W follows the smooth face 26 of thecenter roll 25 into the third nip in the press section, which is a whatis called extended nip NP₃, through which a press fabric 40 thatreceives water runs. The lower roll in the extended nip NP₃ is thecenter roll 25, and the upper roll is a shoe roll 41, in which there area resilient and flexible hose mantle and a press shoe 43 of theextended-nip zone NP₃, by means of which shoe the necessary pressloading and compression pressure are produced in the extended-nip zone.On a lower sector of the center roll 25, after the web W separationpoint, there are doctors 27, which keep the face of the center roll 25clean and which separate the web from the smooth face 26 of the centerroll 25 when the web is passed into the pulper (not shown) placedunderneath, for example, in connection with a disturbance in operationor with threading of the web. From the smooth face 26 of the center roll25, the web W is separated as a short free draw W₀ and transferred ontoa drying wire 60 running over a guide roll 61. On this wire the web W ispassed into the dryer section 3, in which there are upper steam-heateddrying cylinders 62 and lower reversing suction rolls 63.

In the environment of application shown in FIG. 2, the run of the lowerwet wire 10 of the former section 1 in the pick-up area differs fromthat shown in FIGS. 1 and 6. In accordance with FIG. 2, the wet wire 10of the former section 1, e.g. the carrying lower wire 10 of a twin-wireformer, has a gently downwards inclined run onto the wire guide roll11A, which has an open hollow face 11 a. On the wire guide roll 11A, therun of the wet wire 10 is turned substantially straight downwards ontothe wire drive roll 12. In FIG. 2, the pick-up point P is placed beforethe wire guide roll 11A on the gently downwards inclined run of the wetwire 10. The pick-up felt 20 carries the web W into the first extendednip NP₁ in the press section 2, which nip is formed between an upperhollow-faced 29 roll 28 and a lower extended-nip roll 34 provided with aflexible hose mantle 35. At the nip zone NP₁, inside the hose mantle 35,there is a press shoe 37. In the first nip NP, the lower fabric is apress felt 30, from which the web W is separated on the suction zone 36a of the transfer suction roll 36, being passed so that it follows thelower felt 30 onto the upper felt 40 of the second extended nip NP₂,onto which the web W is transferred with the aid of the vacuum presentin the suction zone 46 a of the transfer suction roll 46. On the upperfelt 40 of the second nip NP₂, the web W is transferred into the secondextended nip NP₂, which is formed between a hollow-faced 45 press roll44 and a lower extended-nip roll 51. The extended-nip roll is providedwith a flexible hose mantle 52 and with a press shoe 53. After theextended-nip zone NP₂, the web W follows the lower fabric 50 of thezone, which fabric is a press felt or a transfer belt, by whose meansthe web W is passed onto the drying wire 60 of the dryer section 3 withthe aid of the vacuum present in the suction zone 61 a of the transfersuction roll 61.

As is shown in FIGS. 1 to 5, edge strips WA and WB are cut off from thepaper web W formed on the wet wire 10 by means of water spray cutters110 or, as an alternative, by means of water spray cutters 140. The edgestrips WA, WB are separated from the useful web by means of cut groovesCA and CB, which are seen in FIG. 3. In a normal situation of operation,the edge strips WA and WB are separated, after the pick-up point P, fromthe pick-up felt 20 and follow the wet wire 10 and are guided at thelatest by means of a guide plate 33 into the broke system, such as awire pit or pulper placed underneath.

In the device as shown in these figures, the edge strips of the web Ware kept in contact with the wet wire 10 by vacuum devices 100A and 100Bof a width approximately equal to the width of the edge strips WA andWB. FIG. 3 illustrates a full-width alternative of a vacuum device 100.The vacuum device 100 comprises adjacent vacuum boxes 100A, 100B, 100C.The boxes 100A, 100B placed in the lateral areas of the device 100constitute the intensified suction zones placed at the locations of theedge strips WA, WB, between which there is a vacuum box 100C of themiddle area. It is possible to switch on pressure to the chamber 100C inorder to facilitate separation of the web passing to the press sectionat the time of threading and also during constant operation. A preferredembodiment of the method of the present invention includes instantaneousswitching off of the vacuum in the vacuum box 100C of the middle arearight at the beginning of threading. By means of this method, it ispossible to improve the quality of the tip of the web W during threadingand also in connection with cutting off when the vacuum of the middlevacuum box 100C is switched on at a suitable stage.

FIG. 3 illustrates the pick-up suction roll 21, in which there is asuction zone 21 a. The pick-up roll 21 has been mounted from its axlejournals by means of bearing supports 21A and 21B. In connection withthe second bearing support 21B, a suction pipe 21C has been fitted,through which a vacuum is sucked into the suction zone 21 a by means ofvacuum pumps, which is illustrated by the arrow S in FIG. 3.

In FIG. 3, the widths of the vacuum boxes 100A and 100B placed at theedge strips WA and WB are denoted with SBA and SBB. The trimmed width ofthe web W is denoted with the reference SL in FIG. 3. The sum SL+SBA+SBBof the widths can be somewhat larger than the untrimmed width of the webW. The widths SBA and SBB can also be smaller than the widths of WA andWB, for the edge at the side of cutting is more critical. In this way,excessive sucking of the web edge is also prevented.

In accordance with FIG. 2, after the pick-up roll 21, there are pressureboxes 120A, 120B of a width substantially equal to the width of the edgestrips WA, WB and placed facing the edge strips, by means of whichpressure boxes the edge strips WA, WB are separated from the pick-upfelt 20 and guided, for example, by means of guide plates 33 down intothe broke system.

FIGS. 6, 9 and 10 show pressure zones 121A and 121B, which are placedoutside the vacuum zone 21 a of the pick-up roll 21 at both sides of thevacuum zone and facing the edge strips WA, WB, which pressure zonesprevent the edge strips WA, WB, which are placed outside the paper web Wproper to be passed into the press section, from following the pick-upfelt 20.

The various alternatives of equipment of the present invention that havebeen described above and that will be described later can be employedeither alone or as a suitable combination, as required, and to thecombination of equipment it is possible, for example, to add partcomponents when the web speed is increased so that the effects andfunctions supposed to be achieved by means of the present invention canbe secured in all situations.

In the following, the details of the illustrations in FIGS. 3 to 5 and 7to 10 viewed in different directions will be described in more detail.

FIG. 3 shows the equipment alternative 100 shown in FIGS. 1 and 2 asviewed in the direction A indicated in FIG. 1 and in the direction Bindicated in FIG. 2. The suction roll 21 shown in FIG. 3 may be providedwith a drive of its own (not shown), or it may be driven by the pick-upfelt 20.

FIG. 4 shows the equipment alternative 120A, 120B shown in FIGS. 1 and 2as viewed in the direction C indicated in FIG. 1 and in the direction Dindicated in FIG. 2. FIG. 4 shows the blow boxes 120A, 120B placed afterthe pick-up point P, which boxes are placed outside the trimming widthSL of the paper web W facing the edge strips WA, WB and blow the edgestrips, in accordance with FIG. 2, apart from the pick-up felt 10 to asto be guided by means of the guide plate 33 into the pulper placedunderneath. Moreover, FIG. 4 shows the blow boxes 121A, 121B placedoutside the suction zone 21 a of the suction roll 21 at both sides ofthe suction zone, the blow width of the blow boxes being denoted withSB, and the blow width extending outside the width SL of the trimmedpaper web W across the width of the edge strips WA, WB or slightlybeyond the width outside.

FIG. 5 shows the pressure or blow device 130 as viewed in the directionE indicated in FIG. 2. The pressure device 130 has been fitted after thewire guide roll 11 A in connection with the downwards inclined run ofthe wet wire 10 before the wire drive roll 12. The width of the device130 is slightly smaller than the width of the wet wire 10. FIG. 5 showsthe wire guide roll 11A and the wire drive roll 12. By means of thepressure device 130 it is secured that, when the web W is not passedinto the press section 2, the web W of full width can be separatedreliably from the wet wire 10, from which it is dropped down into thebroke system placed underneath. If the web W tends to be separated fromthe wire 10 too early because of the field of centrifugal forces of thewire guide roll 11A, in stead of blowing, a suitable vacuum can also beswitched on in the device 130, in which case the web follows the wetwire better and is not separated from it until by means of knock-offwater showers.

FIGS. 7 and 8 illustrate the end part of the pick-up suction roll 21placed at the side of the suction duct 21C as viewed in the direction Gindicated in FIG. 6. The suction zone 21a is defined between axial edgeseals 124 a, 124 b in the axial direction of the pick-up suction roll21. The pick-up suction roll 21 has a perforated mantle 122 and closedends 123, which have been connected with the axle journals provided withbearings. The suction zone 21 a is defined by a stepped end seal 125 a,125 b, 125 c fitted at the cut groove (FIG. 4) of each edge strip WA,WB. In the direction of progress of the web W, the first end seal 125 ais placed outside the trimming width SL of the web W and completely onthe area of the edge strip WB. The middle end seal 125 b is placed onthe cut groove CB, and the last end seal 125 c is placed inside thetrimming width SL of the web W so that the outer edge of the end seal125 c is placed on the cut groove CB. By means of the steppedconstruction of the end seal 125 a, 125 b, 125 c, which narrows thesuction zone 21 a stepwise at its ends in the direction of progress ofthe web W, it is achieved that the edge strips WA, WB are separated fromthe pick-up felt 20 more reliably even at very high web speeds.

FIG. 8 shows a modification of the construction shown in FIG. 7. The endseal 125 d of the suction zone 21 a is in an inclined position at thecut groove CB so that, in the direction of progress of the web, at thelocation of the first axial seal 124 a, the inner side of the end seal125 d is placed on the cut groove CB, whereas at the outlet end of theinclined end seal 125 d the outside edge of the seal is placed on thecut groove CB at the location of the latter axial seal 124 b. By meansof this inclined construction, the same effect is obtained as by meansof the stepped end seal construction as shown in FIG. 7.

In the arrangement of the end area of the suction zone 21 a of thesuction roll 21 shown in FIGS. 7 and 8, the trimmed paper web W issucked into contact with the pick-up felt 20 in the beginning of thesuction zone 21 a after its first seal 124 a, after which the suctionholes 126 (FIGS. 9 and 10) in the mantle 122 of the suction roll 21 keepthe edges of the web W in contact with the pick-up felt 20 at the sametime as the opening suction holes 126 at the side of the edge strips WA,WB allow the edge strips WA, WB to be separated from the pick-up felt20. This same effect is produced both by means of the stepped sealconstruction 125 a, 125 b, 125 c as shown in FIG. 7 and by means of theinclined seal construction 125 d as shown in FIG. 8. The stepped sealconstruction as shown in FIG. 7 has the particular advantage that eachseal 125 a, 125 b, 125 c can be set independently from the others insuch a location that the operation is carried into effect optimally. Inthe inclined seal construction 125 d the angle of inclination can bemade adjustable for the purpose mentioned above.

FIGS. 7 and 8 illustrate just one end of the pick-up suction roll 21,but it is obvious that a corresponding arrangement of edge seals 125 a,125 b, 125 c; 125 d has been fitted in connection with the opposite endof the suction roll 21 and of its suction zone 21 a on, and in the areaof, the edge strip WA and the cut groove CA in the way illustrated inFIGS. 7 and 8.

FIGS. 9 and 10 illustrate the construction of the pressurized blow boxes121A and 121B placed in the vicinity of the ends 123 of the pick-upsuction roll 21 as viewed in the direction F indicated in FIG. 6. FIGS.9 and 10 show just one blow box 121B, but a corresponding box 121A isalso provided at the opposite end of the suction roll 21. The blow box121B is defined by the inner wall 127 and by the end 123 of the roll andby the perforated 126 mantle 122 of the roll 21. In the blow box 121B,on the end seal (FIGS. 7 and 8) of the suction zone 21 a and on the cutgroove CB of the edge strip WB, there is an end seal 129 a, which sealsthe blow zone 121B against the inner face of the roll 21 mantle 122. Thepressurized end area and the end seal constructions shown can beemployed together or separately. Also a stepped seal construction and aninclined seal construction are possible between the blow zone and thesuction zone. As is shown in FIG. 9, the end seal 129 a has beenperforated over its entire length in the machine direction. Into theseseveral holes, air is fed through the pipes 128. Such a use can bearranged in accordance with a need of pressure or vacuum, which isillustrated by the arrow AF. Out of the pipes 128 and out of the holesin the seal 129 a, air has access into the holes 126 in the mantle 122of the roll 21 placed on the cut grooves CA, CB and on the inner edgesof the edge strips WA, WB, whereby separation of the edge strip WB fromthe pick-up felt 20 is promoted. The construction of the blow box 121Bshown in FIG. 10 is in the other respects similar, except that its endseal is a narrow-tipped seal rib 129 b, which has been attached to thewall 127 by means of fastening parts 129 d. The tip edge 129 c of theseal rib 129 b is placed at the side of its inner side. By means of aseal rib 129 b as shown in FIG. 10, the closed area that keeps the edgestrip WA, WB in contact with the pick-up felt 20 is minimized, while therigidity of the seal rib 129 b is, however, retained. In stead of theholes that have been formed into the end seals 129 a, of course, a setof ducts or any other, equivalent solution known to a person skilled inthe art can be formed into the end seals 129 a, by means of which ductsor equivalent air can be fed through the end seals 129 a and through theholes 126 in the end areas of the mantle 122 of the roll 21 into the cutgrooves CA, CB and to the inner edges of the edge strips WA, WB of theweb W.

If necessary, the above equipment alternatives 100 and 120A, 120B areconnected with transfer devices (not shown), by whose means the devices100, 110 can be shifted in the cross direction of the machine. By meansof these transfer devices, the edge strips WA, WB to be trimmed off fromthe web W are adjusted so that they follow the wet wire 10 directly orthat they are at least dropped off from the pick-up felt 20. In a thirdalternative (FIGS. 6, 9 and 10), the suction width of the pick-up roll21 has been regulated precisely in relation to the positions of the cutgrooves CA and CB of the edge strips WA, WB, and the pressure zones 121A and 121 B are placed directly outside the vacuum zone 21 a of the roll21.

FIG. 2 shows the final part of a former type in which there is noconventional wire suction roll, such as the roll 11 in FIG. 1, but thepick-up point P is placed before the wire guide rolls on a downwardsinclined run of the wet wire 10, which is less steep than in FIG. 1. Thepress section shown in FIG. 2 is of the SymBelt II type. In FIG. 2, theequipment alternatives 100 and 120A, 120B that prevent passing of theedge strips WA, WB into the press section are the same as in FIG. 1. Inthis alternative embodiment of the final end of the former, the edgestrips WA, WB of the web W are even more readily inclined to follow thepick-up felt 20 than in the embodiment as shown in FIG. 1. In thealternative embodiment as shown in FIG. 2, the web W of full width mustfollow the wet wire 10 also after the upper wire guide roll 11A at astage in which the web W is not passed into the press section 2. Thiscan be promoted, for example, by means of a grooved 10 a wire guide roll10A and by means of a full-width vacuum device 130 fitted after the wireguide roll.

In the following, the patent claims will be given, and the variousdetails of the invention can show variation within the scope of theinventive idea defined in the claims and differ from what has beenstated above by way of example only.

We claim:
 1. In a method in a paper machine for transferring a paper webfrom a wet wire in a former section to a pick-up fabric or an equivalenttransfer fabric of a press section, including the steps of forming apick-up point on the wet wire, separating an edge strip from at leastone edge of the web prior to the pick-up point by means of at least onecutting device, and separating the web from the wet wire and passing theweb onto the pick-up fabric at the pick-up point, the improvementcomprising: applying a pressure difference to the at least one edgestrip through the wet wire or the pick-up fabric at or after the pick-uppoint by means of blow boxes arranged within the pick-up fabric to blowonto the pick-up fabric and thereby prevent the at least one edge stripfrom following the pick-up fabric.
 2. In a method in a paper machine fortransferring a paper web from a wet wire in a former section to apick-up fabric or an equivalent transfer fabric of a press section,including the steps of forming a pick-up point on the wet wire,separating an edge strip from each edge of the web prior to the pick-uppoint by means of cutting devices, and separating the remaining web fromthe wet wire and passing the web onto the pick-up fabric at the pick-uppoint, the improvement comprising: applying a pressure difference to theedge strips through the wet wire or the pick-up fabric at or after thepick-up point by means of blow boxes arranged within the pick-up fabricto blow onto the pick-up fabric and thereby prevent the at least oneedge strip from following the pick-up fabric.
 3. The method as in claim1, wherein said step of applying a pressure difference to the at leastone edge strip comprises applying a pressure difference to the at leastone edge strip through the wet wire at or after the pick-up point bymeans of pressure difference devices arranged within the wet wire tocause the at least one edge strip to follow the wet wire.
 4. The methodas in claim 3, further comprising the step of applying a pressuredifference to the web through the wet wire such that the pressuredifference applied to the web is less than the pressure differenceapplied to the at least one edge strip.
 5. The method as in claim 4,wherein the method takes place during threading and during constantrunning of the web, the method further comprising the step of reducingthe pressure difference applied to the web through the wet wire duringthreading of the web.
 6. The method as in claim 1, wherein said step ofapplying a pressure difference to the at least one edge strip comprisesapplying a pressure difference to the at least one edge strip throughthe pick-up fabric at or after the pick-up point by means of at leastone blow zone arranged within at least one side of a suction zone of apick-up suction roll arranged within the pick-up fabric proximate to thepick-up point to cause the at least one edge strip to separate from thepick-up fabric.
 7. The method as in claim 6, wherein the at least oneedge strip is separated from the at least one edge of the web at an atleast one cut groove, the method further comprising the step of applyingair to the at least one cut groove by means of at least one ductarranged in connection with the at least one blow zone to cause the atleast one edge strip to be separated from the web.
 8. The method as inclaim 6, wherein the at least one edge strip is separated from the atleast one edge of the web at an at least one cut groove, the methodfurther comprising the step of applying air to the at least one cutgroove by means of at least one perforation arranged in connection withthe at least one blow zone to cause the at least one edge strip to beseparated from the web.
 9. The method as in claim 1, further comprisingthe step of applying a pressure difference to the web after said pick-uppoint to cause the web to be separated from the wet wire and passed ontothe pick-up fabric if the web fails to be passed onto the pick-up fabricat the pickup point.
 10. In a paper machine in which a paper web istransferred from a wet wire in a former section to a pick-up fabric,arranged in a loop, in a press section in a running direction of theweb, including a pick-up point located on the wet wire, at least onecutter device arranged in association with the wet wire before saidpick-up point in the running direction of the web for separating an edgestrip from at least one edge of the web, and means for transferring theweb from the wet wire to the pick-up fabric at said pick-up point, theimprovement comprising: means for applying a pressure difference to theat least one edge strip through the wet wire or the pick-up fabric at orafter said pick-up point to cause said at least one edge strip to eitherfollow the wet wire or become separated from the pick-up fabric afterthe pick-up point and structured and arranged inside said loop of saidpick-up fabric after said pick-up point.
 11. In a paper machine in whicha paper web is transferred from a wet wire in a former section to apick-up fabric, arranged in a loop, in a press section in a runningdirection of the web, including a pick-up point located on the wet wire,cutter devices arranged in association with the wet wire before saidpick-up point in the running direction of the web for separating an edgestrip from each edge of the web, and means for transferring theremaining web from the wet wire to the pick-up fabric at said pick-uppoint, the improvement comprising: means for applying a pressuredifference to said edge strips through the wet wire or the pick-upfabric at or after said pick-up point to cause said edge strips toeither follow the wet wire or become separated from the pick-up fabricafter said pick-up point and structured and arranged inside said loop ofsaid pick-up fabric after said pick-up point.
 12. The paper machine asin claim 10, wherein said wet wire is arranged in a loop, and said meansfor applying a pressure difference to said at least one edge stripcomprises at least one pressure-difference device arranged inside theloop of said wet wire proximate to said pick-up point.
 13. The papermachine as in claim 12, wherein said pressure-difference devicecomprises a middle box structured and arranged to apply a pressuredifference to said web and at least one outer box structured andarranged to apply a pressure difference to said at least one edge strip,said pressure difference of said at least one outer box being higherthan said pressure difference of said middle box.
 14. The paper machineas in claim 10, wherein said means for transferring the web from the wetwire to the pick-up fabric comprises a pick-up suction roll having twoends, said pick-up suction roll comprising a suction zone, and blowzones arranged in said suction zone at the ends of said pick-up suctionroll.
 15. The paper machine as in claim 10, wherein the pick-up fabricis arranged in a loop, the improvement further comprising a wire guideroll arranged after said pick-up point, and pressurizedpressure-difference devices arranged inside the loop of the pick-upfabric.
 16. The paper machine as in claim 10, wherein the wet wire isarranged in a loop, the improvement further comprising a wire guide rollarranged after said pick-up point, and a pressurized blow devicearranged after said wire guide roll and inside the wet-wire loop.